Slava (coffeemug) is very brave to introspect publicly and whenever I interacted with him, behaved with greatest integrity and kindness. Unfortunately, his hypothesis here that devtools are a tough market does not ring true. Making a business is always tough, making one that does something new is even tougher. There are many tools and database companies doing extraordinarily well, from Atlassian to Cloudera to Docker to Elastic. The difficulties that RethinkDB faced, as it pivoted from closed source MySQL DB backend, to open source independent database with a very cool update mechanism, were in my analysis much more mundane. Simply, RethinkDB was not easy. Here is a flavor of their thinking, when they rejected a REST HTTP interface: "The RethinkDB query language is so simple, expressive, and pleasant, that trying to make it available over HTTP would be quite difficult and a disservice to users."
Developers have a big advantage when making devtools in that they are their own target market. They are, but only at the start of the project before they become embroiled in it. Ironically this feeling of making it for oneself leads to a mistaken urge to thrust complexity onto the target. As an infra engineer myself, this is something I always try to keep in mind -- I worked on a modelling language at a large company and I credit its success to its absolutely straightforward and accessible syntax, lack of dependencies and straightforward integration into workflows. The temptation is always to make sure users are aware of the choices, force them out of bad habits and make them consider the tradeoffs (this Strange Loop talk from Peter Alvaro addresses the social treatment of users https://www.youtube.com/watch?v=R2Aa4PivG0g ). For RethinkDB, it was wrong to try to force people to learn a new language to use a DB, when there are just tons of interfaces already, and the new language has incremental benefits over say SQL.
However elegant the design of software, the deployment that is the largest or most demanding for it will always find problems. There's no point seriously trying to claim great reliability or quality for a nascent project. It's unbelievable. Instead you need to focus on getting it used in some friendly project that is willing to pay the cost of these teething problems for some particular feature. Once battle tested, reasonable tech leads can choose to use it, comfortable that they won't be the biggest deployment (e.g. git bootstrapped by its use in the Linux kernel). Alternatively, and less scrupulously, you can try to bootstrap by providing a very convenient experience at the start of a simple project for junior engineers - there are many NoSQL DBs that promise the world and are incredibly easy to set up (see the https://aphyr.com/tags/jepsen Jepsen blog for many sad examples, RethinkDB proudly did well in this test).
RethinkDB refused to make the market fit compromises necessary. Market fit is about timing. Don't read the Economist. Ship early and keep your users on board through whatever engineering compromise necessary.